Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$203.25	9.367%	$222.2884	$222.29	$222.30	$222.30
Purchase #2	$157.41	7.347%	$168.9749	$168.97	$168.95	$169.00
Purchase #3	$183.25	7.363%	$196.7427	$196.74	$196.75	$196.70
Purchase #4	$42.85	7.754%	$46.1726	$46.17	$46.15	$46.20
Purchase #5	$117.58	7.467%	$126.3597	$126.36	$126.35	$126.40
Purchase #6	$172.54	10.609%	$190.8448	$190.84	$190.85	$190.80
Purchase #7	$42.38	13.282%	$48.0089	$48.01	$48.00	$48.00
7 purchase totals =	$919.26		$999.3920	$999.38	$999.35	$999.40